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SARA-R4/N4 series - System Integration Manual

UBX-16029218 - R13 System description Page 30 of 119

• AT commands according to 3GPP TS 27.007 [6], 3GPP TS 27.005 [7], 3GPP TS 27.010 [8]

• u-blox AT commands (see the SARA-R4/N4 series AT Commands Manual [2])

The default baud rate is 115200 b/s, while the default frame format is 8N1 (8 data bits, No parity, 1 stop bit: see Figure

13). Baud rates can be configured by AT command (see the SARA-R4/N4 series AT Commands Manual [2]).

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Automatic baud rate detection and automatic frame format recognition are not supported.

D0 D1 D2 D3 D4 D5 D6 D7

Start of 1-Byte

transfer

Start Bit

(Always 0)

Possible Start of

next transfer

Stop Bit

(Always 1)

bit

= 1/(Baudrate)

Normal Transfer, 8N1

Figure 13: Description of UART 8N1 frame format (8 data bits, no parity, 1 stop bit)

1.9.1.2 UART signals behavior

At the end of the module boot sequence (see Figure 9), the module is by default in active mode, and the UART interface

is initialized and enabled as AT commands interface only if the USB interface is not enabled as AT command / data

communication interface: UART and USB cannot be concurrently used for this purpose.

The configuration and the behavior of the UART signals after the boot sequence are described below:

• The module data output line (RXD) is set by default to the OFF state (high level) at UART initialization. The module

holds RXD in the OFF state until the module transmits some data.

• The module data input line (TXD) is assumed to be controlled by the external host once UART is initialized and if UART

is used in the application. The TXD data input line has an internal active pull-down enabled on the “00” and SARA-

R410M-02B product versions, and an internal active pull-up enabled on the other product version.

1.9.1.3 UART multiplexer protocol

SARA-R4/N4 series modules include multiplexer functionality as per 3GPP TS 27.010 [8], on the UART physical link. This

is a data link protocol which uses HDLC-like framing and operates between the module (DCE) and the application

processor (DTE) and allows a number of simultaneous sessions over the used physical link (UART).

The following virtual channels are defined:

• Channel 0:

for Multiplexer control

• Channel 1:

for all AT commands, and non-Dial Up Network (non-DUN) data connections. UDP, TCP data socket /

data call connections via relevant AT commands.

• Channel 2:

for Dial Up Network (DUN) data connection. It requires the host to have and use its own TCP/IP

stack. The DUN can be initiated on modem side or terminal/host side.

• Channel 3:

for u-blox GNSS data tunneling (not supported by “00” and “01” product versions).

1.9.2 USB interface

1.9.2.1 USB features

SARA-R4/N4 series modules include a High-Speed USB 2.0 compliant interface with 480 Mb/s maximum data rate,

representing the main interface for transferring high speed data with a host application processor, supporting:

• AT command mode

• Data mode and Online command mode

• FW upgrades by means of the FOAT feature (see 1.13.7)

For the definition of the interface data mode, command mode and online command mode see SARA-R4/N4 series AT Commands Manual [2]